<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>


		<!-- 
		 
		https://zhuanlan.zhihu.com/p/25892372
		 
		 
		 -->
		<style>
			.container {
				border: 1px solid red;
				width: 500px;
				margin: 0 auto;
			}

			.item {
				height: 60px;
				background: blue;
				width: 300px;
				margin: 50px auto;
			}
		</style>
	</head>
	<body>

		<div class="container">
			<div class="item"></div>
			<div class="item"></div>
		</div>

	</body>
</html>
